What is Los Alamos Chess?
Los Alamos chess is chess on a 6×6 board without bishops. Each side has a king, a queen, two rooks, two knights and six pawns, set up as rook, knight, queen, king, knight, rook behind a row of pawns.
Pawns move only one square at a time, even on their first move, so there is no en passant, and they promote to a queen, rook or knight. There is no castling. Checkmate wins, and the draw rules are those of standard chess.
The small board brings the pieces into contact from the first move, so games are short and tactical, and a single tempo often decides the attack.
Rule changes
| Rule | Standard Chess | Los Alamos Chess |
|---|---|---|
| Board | Standard Chess8×8 squares. | Los Alamos Chess6×6 squares, files a to f and ranks 1 to 6. |
| Starting position | Standard ChessRook, knight, bishop, queen, king, bishop, knight, rook, with eight pawns in front. | Los Alamos ChessRook, knight, queen, king, knight, rook, with six pawns in front. There are no bishops. |
| Pawns | Standard ChessMay move two squares on their first move, can be taken en passant and promote to any piece. | Los Alamos ChessAlways move one square, so there is no en passant. They promote to a queen, rook or knight. |
| Castling | Standard ChessAllowed once per game on either side. | Los Alamos ChessNot allowed. |
| How to win | Standard ChessCheckmate the opponent's king. | Los Alamos ChessThe same: checkmate. Stalemate and the other draws work as in standard chess. |
History
Los Alamos chess was created in 1956 at the Los Alamos Scientific Laboratory in New Mexico, where Paul Stein and Mark Wells programmed the MANIAC I computer to play it. The full game was too much for the machine, so they shrank the board to 6×6 and left out the bishops.
MANIAC I played three games: against itself, against a strong player, who won, and against a beginner who had learned the game a week earlier, whom the computer beat. It is often described as the first time a computer won a chess-like game against a human.